Abstract
In this paper, we investigate channel estimation with pilot reuse for massive MIMO with in-phase and quadrature-phase imbalances (IQI). Firstly, we obtain an augmented real-valued representation for the received signal by processing the real and imaginary parts individually with relative compensation. Then based on the obtained augmented real-valued representation, we perform minimum mean square error (MMSE) estimation for the effective channel which comprises the IQI matrix and wireless channel coefficients. Pilots are reused to reduce the pilot overhead. A lower bound of the effective channel estimation MSE is obtained. Motivated by the optimal conditions under which the lower bound can be achieved, we propose a pilot schedule algorithm. Finally, a least square based method to obtain the relative IQI compensation coefficients is provided. Numerical results verify the performance of the proposed effective channel estimation with pilot reuse.
Highlights
Massive multiple-input multiple-output (MIMO) is a key technology for the fifth-generation (5G) communication systems [1]
A lower bound of the effective channel estimation MSE is given
We assume that the base station (BS) is equipped with uniform linear array (ULA) where the number of BS antennas is set to be 128, and the antennas are spaced with half wavelength distance
Summary
Massive multiple-input multiple-output (MIMO) is a key technology for the fifth-generation (5G) communication systems [1]. Based on the augmented real-valued representation obtained with relative IQI compensation, we perform minimum mean square error (MMSE) estimation for the effective channel. We verify that, based on the obtained augmented real-valued model with relative IQI compensation in (18), it is feasible to perform effective channel estimation with pilot reuse and the pilot interference does not degrade the effective channel estimation MSE performance. It can be seen from Proposition 2 that if the UTs with non-overlapping angular domain channels reuse the same pilot, the achieved sum effective channel estimation MSE is equal to that with orthogonal pilots. We can schedule the pilots based on the condition (30) by defining a function to measure the orthogonality between the effective channel covariance matrices of two different UTs as μ( k, ). In order to adjust the pilot sequence length, we provide a pilot scheduling algorithm according to the UT overlapping degree requirement in Algorithm 1
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